By Karlee Weinmann ( May 7, 2013, 1:44 PM EDT) -- Private equity-backed Antero Resources LLC could bring in as much as $10 billion in a planned initial public offering, potentially triggering a huge windfall for Warburg Pincus LLC, which first bought into the oil and gas company a decade ago, according to a Tuesday report from Reuters. The Denver exploration firm has enlisted Barclays PLC, JPMorgan Chase & Co. and Citigroup Inc. to help guide the process. Antero has more than 300,000 acres in the Marcellus Shale and another 100,000 or so in the Utica Shale, two of the most sought-after formations in the United States. While the company has already begun to churn out substantial business from their existing operations, it has said it believes more natural gas liquids are locked within its Marcellus properties, stoking speculation that its assets' worth could tick up even higher. Warburg Pincus, a private equity mainstay based in New York, coughed up $260 million for a slice of Antero in 2003, and four years later led a consortium that poured $1 billion into the business....